1. Field of the Invention
The present invention relates to a suspension board with circuit, and more particularly, to a suspension board with circuit used for a hard disc drive.
2. Description of the Prior Art
A suspension board with circuit used for a hard disc drive is a wired circuit board comprising a suspension board supporting a magnetic head and a wiring circuit pattern, integrally formed on the suspension board, for connecting between the magnetic head and a read/write board to which read/write signals read and written by the magnetic head are transmitted. The suspension board with circuit is now being in widespread use in that it can support the magnetic head, with a minute interval between the magnetic head and a magnetic disk held against an airflow generated when the magnetic head and the magnetic disk run relative to each other, so that it can well maintain the floatation of the magnetic head mounted on the suspension board.
This suspension board with circuit usually comprises, as shown in FIG. 14(a), a supporting board 101 of a stainless foil or the like metal foil, an insulating base layer 102 formed on the supporting board 101, a conductor layer 103 formed in a wiring circuit pattern on the insulating base layer 102, and an insulating cover layer 104 to cover the conductor layer 103. It further comprises an external connection terminal 105 to connect the wiring arranged in the form of a wiring circuit pattern with the read/write board (not shown).
This external connection terminal 105 formed in the suspension board with circuit includes a flying lead portion. The flying lead portion is formed in such a manner that the supporting board 101 and the insulating base layer 102 are opened at the back side of the conductor layer 103 and also the insulating cover layer 104 is opened at the front side of the conductor layer 103, so that front and back sides of the conductor layer 103 are exposed, as shown in FIG. 14(b). In the flying lead portion, a pad portion 108 comprising a nickel plating layer 106 and a gold plating layer 107 is formed on both of the front and back sides of the conductor layer 103 (Cf JP Laid-open (Unexamined) Patent Publication No. 2001-209918, for example).
In this suspension board with circuit, the forming of a fine wiring circuit pattern is usually required for patterning the conductor layer 103 into a wiring circuit pattern. The additive process is used for the patterning, accordingly. In the additive process, after a seed film 109 of conductive material is formed on the insulating base layer 102, a plating resist (not shown) having a reverse pattern to the wiring circuit pattern is formed on the seed film 109 and then the conductor layer 103 is formed in the form of a wiring circuit pattern on the seed film 109 exposed from the plating resist, as shown in FIG. 14(a). Thereafter, the entire surface of the seed film 109 is removed, except a portion thereof where the plating resist and the conductor layer 103 are formed (Cf. JP Laid-open (Unexamined) Patent Publication No. 2001-209918, for example).
In the suspension board with circuit including the flying lead portion, when the conductor layer is formed in the wiring circuit pattern by the additive process, there is a possibility that the conductor layer and pad portion exposed in the flying lead portion may be damaged in the additive process. This is because since the additive process involves various production processes including the treatment process using a treatment agent and the washing process using washing water, there is a possibility that the conductor layer and pad portion exposed in the flying lead portion may be physically damaged directly, so that the conductor layer and the pad portion may be broken in the processes of the additive process. Particularly in the case of the conductor layer exposed in the flying lead portion being required to be thin, the possibility of such a breaking will increase.